Jean Evrard (CNES), Gilles Roudil (IRAP), Peter von Ballmoos (IRAP) 7 september 2012, LAL current gondola design changes based on - requirement for tunable lenses (6 th prog. meeting) - splasdown proof instrument (CSTB decision) - versatile thermal design (thermal meca meeting of 4/9) a pathf inder mission for JEM-EUSO EUSO-BALLOON 1

motivation : drop test of the LPMA/IASI on 26 June

Splashdown-Strategy In order to maximize the chances for a dry recovery of the EUSO-BALLOON electronics (PDM, DP and CNES subsystems within the “booth”) after splashdown, the following strategy is proposed A) after splashdown, a number of independent schemes avoid that water is getting onto the electronics I) Floatation collar maintaining the instrument-booth above sea-level II) Leaktight instrument-booth III) Backup for failure in I and/or II (insubmersible booth, side walls are clear of electronics) in order to keep the above schemes operational on splasdown B) efficient deceleration shall minimize damage to the payload, particularly w/r to cracks/leaks in the instrument booth in the case of water landings. 3

A) Floatation collar maintaining the instrument above sea-level The instrument is surrounded by a floatation collar (-> Mercury/Gimini/Apollo capsules) that maintains the instrument booth above the sea level. Altough the immersible part of the instrument may (partly) serve as stabilizer (if the center of buoyancy can be held sufficiently above the center of gravity) the “float” will be stablilized by its horizontal dimensions (collar on short outriggers, if needed). The efficiency of the deceleration (above) is important for the viability of the floatation collar. detailed design of (exterenal) floatation collar not an issue here 4

A) Leaktight instrument-booth Using lens 3 as porthole is making the instrument booth watertight. A seal between the lens 3 and platform 3, running inside the nose of the spider (see Fig) plays and important role in this. Again, the deceleration (above) is crucial for the practicality of the integrity of the structure, the tightness, and particularly the survival of lens 3. 5

A) Insubmersible booth and side walls are clear of electronics In the case the above techniques should (partially) fail, a backup be based on rendering the instrument booth “unsinkable” (as certain shiphulls). This should be most easily achieved by Styrofoam panels on the booth’s housing. Since water may likely find its way into the phone booth, a mitigation could consist of placing the electronics components away from the outside walls – such as the PDM which should then stay above the water 6

Protection against capillar water in the insubmersible booth optics-bench and floaters (=> insubmersible) not shown all electronics mounted on the "dry" shelf, clear of outside walls > 5 cm safety-distance to outside wall Limbers 7

Declaration options studied by Jean 8

Jean's baffle/piston simulation Lenght of baffle : Lo (m) :1.00 (=> allows for ±6° FOV) Timestep Dt (s) :0.005 Initial speed dZo(m/s)-6.0 (worst case – 1 chute open only) Ø of the 10 holes St(m2) :0.07 seems to be OK for PMMA (safety-factor 3) Lens 1 survives ! TBC 9

BUT : FLOATATION = INSULATION => OVERHEATING all electronics equipment is installed on the "shelf" (separator) made from Al, and serving as heat-conductor the backwall of the booth is a 1 m 2 radiator again from Al for "cold flights" there is the possibility to add insulation (or heat...) requirement for an efficient cooling (particularly for warm flights) or "cold flights" "warm flights" 10

assembled instrument w/o floaters & crashpads translation stage L3 fixed/tight L2 adjustable (tight) L1 adjustable Baffle & “Piston” radiator electronics on conducting "dry"-shelf window 11

assembly-sequence : the fibrelam instrument-booth 12

"Conduction shelf" and radiator radiator "Shelf-Conductor" for Electronics 13

"Conduction shelf" and radiator inside booth Limbers : Holes forming a passage for the water moving along the sides of the booth 14

"Conduction shelf" and radiator inside booth flange for Lens-3 15

assembled instrument booth - open for integration 16

optics-bench with baffle/piston open instrument booth independent integration/metrology for the optics on one side and the PDM and associated electronics on the other side 17

optics-bench with baffle/piston closed instrument booth calibrated evacuation holes covered with light-tight milar film Baffle & “Piston” 18

... and the IR-Cam, of course the objective of the IR-CAM must be sufficiently high above the roof-rack in order to avoid the baffle 19

assembled istrument (w/o floaters, crashpads) 20

assembled instrument w/o floaters & crashpads L3 fixed/tight L2 adjustable (tight) L1 adjustable Baffle & “Piston” radiator electronics on conducting "dry"-shelf porthole IR Camcalibrated evacuation holes covered with light- tight milar film 21